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Electric Elevators 



WITH DETAILED DESCRIPTION OF 

SPECIAL TYPES 



BY 



FRANK J. SPRAGUE 



Sprague Electric Company 



NEW YORK 



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CHICAGO 






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ELECTRIC ELEVATORS. 



The I: been so much written on the subject of electric ele- 
ati which is pertinent to the subject, thai in pn mting this 
paper I shall make free compilation from others, and, supplement- 
ii, II e ixtracts with some new matter, I shall by lantern views 
illustrate ome details of the more recent machines, then aethocl 
;' manufacture, and some teps in their development. 
The time has pas ed when any one can doubt thai one of the 
him i important applical as of th< ectric transmi i.m <>f power, 
and o in the Dumber and variety of its applications already rival 
j D g the elei trie railway work which has made such marvelous tride; 
, | l( . |i;l ., e ioht ars, is thai of tie operation of all classes of hoist- 
ing ma dnery.. 

»}ome ide of the extenl of the presenl elevator business ma) 
I,, gathered from the Eaci thai in N*ew York City alone there are 
i,,.i i, than •' >00 elevators of various kinds, more, in fad than 
there are streei cars, and more people arc carried vertically than 

there are horizontally. 

I toring for the moment the specific methods of application, ami 
ntine the difficulties culturally met in developii machine 

_ 

to do th 'Ini required in modern office work, ao1 alone the tech- 

D j lifficultii hut those conn trial ones aaturally mei when 

i ip w company enters the list- with untried machines against tin 

itrenched forces of existing industries, there was still much oi 

encouragi n1 to he derived from a backward glance at the indn 

trial cha wroughl in the last few 3 re, ami to all objection 

1 ,1 there 1 ..me the natural queries: Is the elevator field 
;• m alread] is, limited to the possible application of a water or 
1,1 motor? Is there no wider, no more unive al applical n 
of powe 1 for this eh ' service than has ! itherto been pr( ated 
I 1 hydraulic elevator the one bulw b to stand up againsi the 
ultBofthee trie giant? Doesitpn nt such fixit de :n, 
anil f pnrposi refinement of pro* ses, economy of operation and 
freedom from accidents as to preclude the improvement of usin 

oi I htci" power? 






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The elevator field, indeed, is a large one, and if the system is 
electric, then, considered from a commercial standpoint, there ap- 
the following possible classes of work: 
1st. High speed passenger service where no hydraulic plant is 
possible because of limited space. 

2d. Eigh speed passenger service in competition with hydraulic 
plants, the electric plant doing equal duty, costing les-, occupying 
li ipace than the hydraulic, and costing much less to operate. 

d. titution of new high-speed electric sen e in place of 

old -i hi and slow hydraulic services in buildings where the limited 
e and interference with operations will not permit consideration 
of a new hydraulic plant. 

llli. Pass< if- r elevator service in buildings where the Loads are 
< omparatively light. 

5tli. IVi uger service in private houses where safety, -implicit 
and noise] mess are essential. 

6th, !'i -lit and special cl ses of work. 

For om ace we may cla ify elevator work as "first-class, 
thai requiring spi Is from 300' to 600' a minute/' including the 
first three duties above mentioned, and as " ml class, those 
pequiring p ds of from 50' to 250 a minul " which include the 
remainder. 

In neral, there has been required and developed two ki Ls of 
ma< Ines to form these servii es. The firsl is the outcome of the 
inc] l h -lit of buildings and the demand for high sj d and 
d >oth tnotio] largely regardless of cosl of apparatus, space occu- 
pied, or cost of operal ion. 

'Idie hydraulic elevator was the result of this demand, and was 
tl mlyon thatuptoa ear or so ago was acc< L for this service. 

I' k to t this demand — h\ creating an electric elevator 

li would do the work equally well if not better, than the hy- 
draulic — thai the elevator to be more specifically described, was 
'h>l I under some unexpected difficulties. 

Of com such a machine must have the speed and capac v 
of the hydraulic elevator. 

1 1 me be absolutely safe. 

J( should have advantages in the matter of . and must be 

domical to operate. 

Thi -end class i i elevator work, that which requires lov ■ 

s] applied to small apartment houses and other buildings 

win Lighter elevator duly is required. This, for a long time, has 

fairly supplied by worm gear elevators, and the replacing of 



6 

the steam engine by an electric motor has enormously broadened 
the field for this class of machine. 

These two machines, however, are not equivalents Oiey pre 
ent two distinct kinds of rope movement, two absolutely ditteient 
methods of control, and two varieties of safeties 

Jnst here I will briefly outline some of these deferences for ihey 
constitute in my mind vital essentials, and are absolutely deter- 

minate in their limitations. 

The rope movement on the hydraulic is provided by an expanding 
set of sheaves on which all the ropes are maintained in fixed planes 
Four to six ropes can be used on the machine, and six to eight 

on the car. . 

The sets of rope can be equalized at the machine, and they have 

a fixed lead in the hoistway. 

The machines can be double and treble decked, and they have 

absolute limits of mechanical travel. 

All of these features are of the greatest importance when dealing 
with high lifts, large powers and fast travel. 

The drum machine, while having a distinct field of its o n, and 
a most u Enl one, 1 not a single one of the characteristics men- 
oned. It cannot well use over two rop on the drum and they 
cannol be equalizi I at the machine. The 1< d is a shifting on. 
and on long lifts this may be as much as from four to five feet. 

Th ular objections have been met in a type of machine 

whic fc ma all ible drum machine, whore the drive is by 

friction the ropi in the sheave grooves, but in both these ma- 
chines, the plain drum anil the cable drum, there is the vei grave 
objection that there are no fixed limits of mechanical travel which 
are independent of the armature movement, and on fast speeds par- 

lis is absolutel; essential. 
In tl ,. machines the drivi power is applied throng i one 

or more worm gears. 

In mv own praci o Light service, such as 1 asi at hmiatic 

m I a low cli t freight wori I us< a • ugh gear wit) 

all thrust ■arm. on heavier work, a righi oid lef 

hai C i i tin Eindli I- o. m give the Eullesl 

am ax su] and with the shafts onnected by inde- 

. {ii xr .no. which alio* tin worm g s 

to ta '"in h <«ther. 

There is another m< on — that of control. 

The hydraulit machine s necessarily a gravity machine. ng 
pov nlv in hoie in speed on tb dowi sideb :< rolled 



7 
l»v the rale of wateT exit. The machine is, of cour under eounter- 

V _ I d. 

In the 1 1 rum machine, when there is an) r attempt at i- tomy, over 
counl _ liting is gen* rally used, pari from the ear and part from 

back of the drum, the over counter-weighting being approxi- 
nately equal 10 the average load. 
Will) these two i; pes of apparatus as precedents, the problem was: 
How far m electricity be applied? What are the limitation 
i conl rol? What the conditions of installation and operation, and 
to what extent could one type be eliminated? 

And the answer is: Both types must be used, but for distinct 
lassi I -■ ce. 
r J mg the drum type and considering electrical control on 
nine over-balanced for average service, the load up or down 
1 om mes with and metimes against the machine. '['«• control 
li ' machine directly from a supply cii lit (and I cannol seri- 
consider any other, no matter how in mious or refined, a 
aeetinj general conditions), there is one method only, I ilia) is 
the of a rheostat in starting, and the invei variation ot he 
1 I'll 1 of the shunt field for about a two to one variation in speed. 
\ cumulative series coil is only permissible in starting if variatio 

< ontrollable, and in any event thes variations are 
limil I. Such a machine is, however, the b ( for second las 
s> 

Ever me is familiar, of course, with the condition- of ordinary 
freight v rk. I might, however, here point out an if lortani 
branch of this industry, and one which is destined for very wid 

ilication, and that is automatic house service. th< machine to 
1 controlled without an o rator, and so installed as fc< 11 d 

stairway. 

Briefly such a machine, on my system of working, Is equip 
^ I 1 interlocking switch device on the machine, having a co- 
< linat movement with it, and with the controlling circuit in 

• es with a number of door switches automatically opened or cL >sed 
with the doors. The doors themselves are fitted with mechanical 
I illowing a ear to be opened only during a ra n. of mi nent 

rom 6" above to 6" below. 

^i l floor a single controlling button. I the machim is 

rest, the pn ag of a button calls the 1 r, wherever it mav he, 

I the p alar floor ai which it is wanted, where it automatically 

When the door pen it ninot be started, and when run- 
ning, no one else can call it from the flo r for which it ^tined 



8 

The machine also has an additional control in the car and the 
safeguards attending its operation are such a. to make it sate lor 

servant, nurse, child or invalid. 

The development of the multiple screw elevator was undertaken 
for the express purpose of supplanting in a large way the former 
standard for high duty office service, and although not by any 
means an easy problem, either electrically or mechanically, a knowl- 
edge of what the hydraulic elevator is and the variation of the types 
ling, gave adequate reasons for its attempt. 

Let us consider for a moment a hydraulic system, and institute 

a few comparisons. 

It consists primarily of a steam cylinder, or a multiplicity oj 
steam cylinders, working ordinarily under poor conditions of steam 
conomy, hat is with feed cut-off in the high pressure cylinder 
of a compound pump or no cut-off in any cylinder of a simph pump. 
This element, corresponds to the cylinders of a steam engine in 
thi ele< ic e stem, which use steam expansively with a cut-off 
varying ax big to the load, and under pressure conditions which 
are imewhat better than exist in a pump. It is to duplicate the 
results of this system of variable cut-offs and steam expansion, that 
ti, ene E the various pump builders have been more or lese 

men ally bent for a great many years in plain acknowledgmeni 
f thai d i m their simple and duplex pumps, the latter of which 
is common to almost every hydraulic plant of any size in the I nited 

It - fcrue that a so-called " high duty " pump with equalizing pis- 
ton is used on some of the L i ator plants, but its use has not 
proven j any mean- entirely su essful. because of the spasmodi 

nature of the service. 

Among the high duty pumps, the flywheel type, -neb as i> u-d 
on lai _ wa1 pur ting bas been attempted, Inn rarely, 

1 mav fairly say, with sua ess. 

The next element is the water cylinder, which cor responds I 
tl dynamo in tb el< t'ic system, and on account of the high Eri< 
tion le to the pacl the efficiency of a water cy] c with i 
valvi - i i. ordinarily equal to that of dyn q . which with 
r, ids ton ty the typical example of an effi< ent i erg} 

vert 

The nexi elei tin pip - '< the nks, - ession or 

md ] baps imuls r, into oi thr< :li which th< water 

for i liv< the controlling ralvi ' the elevator, 

that wlii rr< - - this in the eled stem is its 



con- 



9 

nnple firing, and if a storage battery is used, then this last in 
conjunction with it. 

Any competent engineer knows that, measured by standard prac- 
tice, a iverj number of pounds of energy can be delivered to the 
rolling apparatus of an electric elevator for less pounds of steam, 
that is, water evaporated, through the medium of no less than fifty 
■ ombinatious of engines and dynamos, than can be delivered to th 
varvi of anv hydraulic cylinder through the standard pumps per- 
missible in average elevator service. To be specific, the average 
v '' ' ration on a compound duplex pump, which is almost 

universally used, will in practice, be not less than about 60 to 70 
pounds per horse-power of water energy delivered to the com rolling 
val . whereas the electric combination will easily give the same 
I'm I than 40 pounds. 

There are t eptional conditions in which a higher economy can 
be gotten in a hydraulic system, but they are few and are not typical, 
a I undt equal conditions the steam consumption in an electric 
!i can be cut in two. 
But this is not all. The fact is persistently ignored, although I he 
ttempt is made to offset it by recent experiments with a differ 
tial piston, that a standard hydraulic elevator use- the same amount 
of r under the same pr< sure for every foot of travel ;i ear, 

which volume of water and pressure are determined by tie' maxi- 
mum lead which has to be carried, although the average Load 0] 
the ro] including the excess of car over counter-weight is not 
r one-third of the maximum. On the other hand, the electrii 
itor uses, and must use, under normal conditions, curreni di- 
ced ! proportional to- the work, modified in a small degree by start- 
ing and slow running. 

In 3hort, over and above the friction load of the generating sys- 

o 

tern, the steam consumption in the engines and the generation of 
tricity in the dynamo vary with the demand of the elevator 
machim It is a s\>tem which is of nee ity automatic. 

1 ' ! t the other hand, the hydraulic i m is one of the most flagrant 

violate the relation which should exist between demand and 

apply. It is a system of transmission by water, having at one end 

aerating plant doing full duty for every foot of travel of its 

piston, with a variable duty on an elevator car at the other end. 

ad an intermediate straight line water engine with its pipes and 

tanks taking care of that variable duty and using the balance of 

-mi in heating the water which passes through its valves. 

Lack of economy, however, is not the only objection to the hy- 



10 



draulic system when looked at from the architect's or Wider* 
tnloint Until recent developments, these have always been 

Shr handicapped, not so much perhaps in the matter of cost 
, u n the internal arrangements of the building as well 

^ ut of the basement, neither of which could be final y and sa - 
Sactorily, if even then, determined, until the particular type of 
id n had been accepted by the owner, and the contract tolly 



made for it. 



Nor has there been either single* - of design or unity of plan 
„f operation. 1 eh maker has had his own form of construction, 

dal method of cm -ol. Every building has hrought up a 

prohl, i more or less nev or at least conditions which had to be 

seriously considered in determining the elevator -mce. Hor,- 

| an a vertical machines, in hasement or shaft;, ugh or low 

amplications; long and short, single and noted cylinders: big 

and little dian* ; large and small sheaves; free and suspended 

C ounter-we bts; pulling and pushing machines; direct and differ- 

I M ,. ,,,„]' tanl . stand pipes, accumulal - and compres- 

iHl high ad low pressures; hand rope, wheel or pilot-val 

,] : simple or compound pumps-all fei made a nightman- 

.mplications, g ng more initial and continuing source of com- 

,„1 disp: than i the other engineering problems m a 



building. 



So wl I more nai a] than that they should turn to ele, 
f 0r ition? And this tendency is augmented by other rea- 






- I 

I out ntral stat a suppl always, when properly 

to d when the el v ice is of a spasmed 

liD dehan . d considering for the present those laa 

L characterize the mod n office or to el buildii. n<1 
,1 , ral • i engine rl ^ that the ev 

, , ,,. f |i-p 1 in s, the more alike fcto •• 

then Qd 1! ater 

my , ,D mill «i. il better the 

, for pov ] ' on - n0 ,mU " c xvl,: M3 

character- 

The b toden m iui1 ' u l 

I dynar : t I;, iting a buiiaing. Th e 

s L ei al rela ag I* i tl i auml t of Li 

edii W i" L (1 the ' 

in ad ion to t • • "I' :1 buildii] 

ad el it is m I o n. v LI Bhall add 

L d< rating plan' 



. 



11 



All thai: is required is that the three units should be somewhat 

ii reased in size and. chaps, one of them preferably divided, the 

mains all taken to a < anion switchboard with two-way switches, 

and ry engine and dynamo thus made interchangeable on either 

lighting or elevator circuits, and at times both, especially if 

using a slow acting corrective converter, some of each can be run 

from the -ante engine and dynamo. So, instead of five or six units, 

me water and some electric, the entire generating plant is re- 

duc I to a single system consisting of three units of one size, or 

two of that size and two of a half size, which can be run inter- 

eably, and one of which is almost always in reserve. 

Just here it is well to consider the probable application of the 

batrery which, if built with plenty of lead, with large sur- 

aces and for heavy momentary discharges rather than for long time 

steady discharges, will prove a most important adjunct to elevator 

which, like railway work, is spasmodic in character. 
A modern ofli ce electric elevator on actual average servi< r< < j uli 
a nditure of about one kilowatt hour per car mile of travel 

for every eight or ten feet of platform area. A car will make from 
11 to miles per hour, so that a battery of six elevators will run 
from 9 to 15 miles, although very rarely making o"\ r 12 miles ;>er 
hour. With an ordinary car, say from 30' to 35' area, this would 
mi an from 3 to 3J kilowatt hours per car mile of travel, or say 
to 40 kilowatt hours for a battery of six machines. Without a 
battery this would require a 120 kilowatt machine as ordinaril 
rated, worked at an average of 3. 5 to 40 per cent. load. With a 
pro rly constructed battery a 60 or even a 50 kilowatt machine 
will handle the elevators. 
Roughly speaking, a storage battery should be able to -rand twice 
dynamo rate for from three, to seven or eight seconds, and the 
lynamo rate for one-half a minute. If it has an hour discharg 

equal to the dynamo capacii in kilowatt 'hours, it should 
ii peri try capable to run the Saturday, Sunday and night service 
required in an elevator plant without losing more than one-half 
its charg 

) much for the general conclusions on electric elevators, which 

essarily more or less brief. 

To meet the hydraulic machine there was dc-igned and developed 

what is now known as the Sprague-Pratt multiple sheave electric 

screw- elevator, following the general lines of a tension hydraulic 

i bine in the matter of rope movement, limit safeties and method 

con >1. 



_ 



12 

The net result has been, that this machine now stands the su- 
perior to the hydraulic elevator in that it has its speed and capacity 
with, if anything, greater safety, and certain advantages in its auto- 
matics. . 

On high lifts it occupies less space; it is more flexible m it- ap- 
plication, is more economical to operate, and it is more easily 

cared for. _ 

General Description.— The machine may be described as the com- 
bination of two old elements with one new one, with specific safeties 

and methods if control. 

Briefly, it is of the horizontal multiple sheave type, with a travel- 
ing C r id and frictionless nut driven by a screw revolved by 
a w or dii tly connected, and governed by a pilot motor and 

l ' 1 1 1 * i v ^ 1~ 5*^ r 

The general cor ruction consists of a heavy main beam, carry- 
ing the traveling erosshead ad the lower rew bearing, with sp< lal 
tings bolted at each end, one carrying the fixed set of sheaves, 
in,! the other thethrusl bearing, brake and motor. The regulating 
apparatus is ind Ldent and self-contained, and is placed on (lu- 
ll. 1" m the car to the system of multiplying sheaves the dir< I 
multiplying machine and the horizontal hydraulic eli atoi are 
practi ii -dim-. The erosshead, however, marl the point of 

d, parture in the two types. 

In the hydraulic machine, this crosshead is rigidly attached to the 
end rod which terminates in a piston moving in a Linder 

t inside length equal to the lineal movement of the ( 
head. This cylinder in the vertical type of hydraulics var com 
30 to 50 I length, with from 2 to 12 sheave multiplications 

and the horizontal types the multiplication runs as high as l I 
with corn mdi diminution of length ol Lind< i and increase 
in cr ion.. Whatever the gearin how er, the length of 

cylinder is a function of tto cai travel. In this electric levator 
the cr< ! being moved alon a rew tionary so far a- th< 

li] )) nio -nt acerned, there i^. with any given number 

ui ... es — only oi triable — tl • agth of si r< ; and, for all 
1 i00 t eL m hine has an advantage 

an of length, which, with incr< I ria . b onu 

importance. 

1. o the d ice btiil i b, there lias bi n adop d 

r\ Is o ropi multiplication, del mined by ili«- heigh.1 of 

buildinj md that sngth of i ichine over all, shall 

i d about ...... appro - ( ' J'« i act ual r 



13 

travel. From this the length grades down to about 21 feet, so that 
all rises between 60 and 300 feet can be taken care of with an ex- 
fcreme variation of nine or ten feet in the length of machine, and 
there is thus provided limiting dimension data of great convenience 
and utility. 

These systems of multiplication I may term direct and indirect. 
In the former, the entire multiplication, varying from six to ten. 
done ,ii the machine, and the ropes lead from the end sheaves 
oveT the shaft sheaves direct to tin- ear. A free counter-weight is 
ii I, the ropes being fastened to the car frame. In this method, 
which is that common to all horizontal and to many vertical hy- 
drauli" machines, the hoisting and counter- weight ropes have un- 
qnal duty; furthermore, the ropes having the maximum bending, 
travel on the outboard sheaves ;it the same speed as the car. Tin- 
last is the ease also with all vertical hydraulics. In some of the 
latter, the counter-weight is carried in the cylinder on the piston, 
in tic strap, or both, its weight being as many times that of a 
free counter-weight as there are multiplications. Sometimes both 

i (hods are used. 

K noniy of operation and smoothness of movement, however, 
a antagonistic in their relations to the amount of counter-weight 
carried. The best method is probably that used when there is a 
single multiplication in the shaft, giving a two to one counter- 
weight traveling at half speed, and carried by all the car-hoisting 
rop is is done for short-rise vertical hydraulic elevators. 

For long rises I have adopted a combination vertical and horizon- 
tal machine rope practice, giving even a more compacl machim 
a longer life of ropes, and better counter- weight results. 

In this indirect system there is a division of multiplication, which. 
while having the same effect -" far as speed of car and Length of 
machine are concerned as a high direct multiplication, has an en- 
tirely different result in the wear on the ropes ami the amount 
of ounter-weight which can be carried without jumping. 

This is accomplished by making one-half the multiplication (6 or 
8) <m the machine, the ropes, properly proportioned . going thence 
to the bottom of the counter-weight frame, which has a single 
multiplying sheave on top. The car ropes go over the shaft sheave 
mi' i the counter-weight multiplier, and back up the hoistway. 
win n the are anchored, 2 i ving a car speed twice thai of the counter- 
weight. The equalizing chains, used to make the pull of the car 
witti any given load constant at all points of the hoistway, are 
fastened to the bottom of the counter- weight frame and anchored 
in the hoistway. 



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is taken on balls and the sheaves are carried on ball or roller bearings, 

This nut being a vital part, it- development lias be< n most thor- 
ough, and a | iliar treatment of steel which has been adopted 
renders its surface so hard that the wear is very small, and it is 
well within commercial limits. 

So free is the machine fron static friction that it is possible 
to start the car with a very slight increase of current over the 
normal hoisting current, providing time be taken bo that the work 
done in acceleration is .-mall to the work of lifting, although that 
is not the usual practice. 

Tl lis have an average crushing -train of £5,000 pound- each, 
but the working pressure varies from only 50 to 125 pounds per ball. 

The nut system is a compound one. for, besides tin working 
hall nii: thei s another, called tin ty-nut," to which I will 

make refei later, 1 d i and between the two ie a powerful 



Qg under eomj ion. 
Tin w a I- I bar i bigb carbon steel with •nliarly 

thread, the finished - ev» bavii a tensile strength I 700,- 
000 pounds. It passes throu i th< c] irari hold in the sti 
trunnion I. which ear the traveling sheai . then 

liroi _Ii J it. and i t1 il outer end b 1 i fixed 



SIBMCAS 




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This sen i»eii tied to tin armature shaft b 

on y i gib. 

'I end • the ; rmal ur< -I) : . which < '.'< < I th 

i . I- thn id . u here i 

n b i 'o balls cai in a bron; g i le 






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j, l.r hardened I The thi 

)h .. ip o tie in-b.i )tl. • 

tl thai 

1 — I i , it if ah • n -i rai 

ji mnot buck] i 

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17 

pi uliar. They form a path for themselves, partly by wear, but 
principally by rolling compression of the steel, which finally be- 
comes exceedingly hard, such that the edge of any ordinary ma- 
chine tool would be turned. 

Tin' halls themselves wear very evenly. Oblique forms in normal 
practice cannot exist. 

Beyond the thrust-plates is keyed an iron pulley, connected by 
a flexible coupling with the motor shaft. The function of the 
braki is thai of locking the screw when at rest, it not a means 
of varying th speed. In case of accident, it has the addittolial 
function of helping to stop the screw. It may be described as a 
coi mid i sctro-mechanical brake. A steel brake band, wood- 
lined, is anchored at one end, the hoisting-side on the motor-bed 
| frame <i the other end is continually pulled down by a power- 

in! spring under compr< ssion. The mechanical movement in oppo- 
I sition is through the medium of a peculiar magnet, li is operated 

I 1 a dual circuit, one in hoisting, another in lowering. In the event 

I i failure of current for any reason, or too high a speed on the down 

I run. this magnet releases the brake m the latter case by a snap 

cli. operated by an adjustable Pickering centrifugal governor 
drivi i by the main screw — and the brake band pr< mptlj grips Hi 
l)i wheel softly yet powerfully. 

.1/ tor. — -The motor, which is of the multipolar type, is carried 
on the same easting which contains the thrust bearing. The field 

magne are of E 1, and are i d by two circuits; one, known 

as the shunt circuit, being variable in strength at will, so as to 
vary th maximum speed of the machine, and the other, a serii 
circuit, which acts to strongly compound the field. This type of 
eh itors is differentiated from all other el ctrics bv the fact that 
11 action is like that of the hydraulic, for it alwavs work- n -t 
I gravity. In hoisting, the motor takes current from the line, but 

in lowering, it- main circuit is cut off from the line, and the 
motor, rotating in an opposite direction, is driven as a dynamo 
i th .ill of the ear. A strong element of safety exists in 

the hi i hat the current in the field coils is never reversed, and 
quently the machine is n er demagnetized. Ilenc Lder cer- 
tain conditions of the operation of the safeties, it has a iwer of 
si lf-< .i it a t ion which is of importance. 

Tin armature which turns in this field is of the ironclad type, 
•, 1 not liable to injury of any kind. 

ll is mounted on a sleeve, is of the 2-path series winding, has 
a ver . large commutator, and, of course, multiple carbon brushes. 



18 



The field coils can be i. moved without disturbing any other 

art. 
C\,,;//-0Z.— Considered in its simplest form, and in connection 

with its action upon the motor and multiplying machine,, without 
reference to the means of communication between the car and the 
regulator, this last is a verv simple device. It is composed of two 
parts, each made up of peculiarly shaped iron grids of various sizes 
arr. d in circular form, connected to copper contacts on a slate 
disk over which passes a heavy carbon brush. 

The use of iron castings of a specific composition possesses greal 
advantage over any form of wire resistance . not alone in the matter 
of cost. They are flexible, tin < pand in any direction readily 
and, as made, they have a resistance of from forty to fifty times 
that of i opper, or roughly, that of German silver. The grids are 
interchangeable d any of them can be rea ly replaced. 

On« • of the rheostat is for n illation in hoisting, the oth< c 
for low Ing. Instead of moving this regulator by hand. ,it is 
, rat.d by a pilot motor wound with a right and left handed 
j: ,!. oni the other of which only at a time, can be in nit 
with the armi re. This pilot is connected to lite rheostat arm b 
le reduction worm gear, and is operated either from th 
) to In ir. a< irding t« i he position of the " change over " 

S v it< !i. by an up " 1 " down w buttoji v b an autom i per 

op which n mally hi to he I < Id by the operator to prevent the 
pilot returning to a -top position. The spindle of I e rheostat 

p m op switches i ordinatii in tb ■ cment, in turn 

controlli th< -ua. tic make-and-break < tswii ■ te down 
1 ud i tie automatic stop level lies which Limit t he 

pili m lit. 

'I r i ..'tie swil it ad of hand ol switch* 

remoi an ng from i foc< o eo it, bul 

th( ■ • >ui i oflfe a | hie by ~ oth< i 

means ol. 

'i si- E tin i m >oi I (he | 

i) a i \n " up " mol md an 

• i t fright 1< '1 

ill o|] da!'. i Jull" 

i i hi i c i 

■ hi. movemc Li I 
about hold th d lift tl 

Thie then ll\ i. i!i< i 

. mxh ii. m< 






19 

ment with an acceleration depending npon the rate of movement 
of the rheostat arm, and with a final velocity determined by the 
point at which the arm is stopped. 

If. while hoisting, for any reason the current is cut oil', the tor- 
Ional effort ceases, the brake instantly comes into ail ion and the 
ar comes to rest- 
In lowering, the brake is lifted by an independent circuit, but 
the armature is first short-circuited on itself, and becomes a most 
powerful dynamic brake. As the resistance in this circuit is in- 
creased, the car runs faster. When it approaches the lower limit 
01 movement, an independent retarding circuit is established, and 
gi lually reduces the resistance. This brings the car to the slowest 
movement. 

The pilot movement regulation is, to my mind, an absolute ne- 
e< of fast passenger work; and its application, although at first 

attended with a number of annoying difficulties, is to-day by far 
the most reliable method of control known. 

Saj es. — Of course, the vital question to be considered in any 

elevator system is that of safety. In that respect, I think, we are 

amply provided. Safeties may be considered under two heads: 

I: j rst, those on the car, and second, those on the hoisting machine. 

On the car we use a special centrifugal which is attached to the 

lower section of the car frame. 

It consists of two long levers, short-fulcrumed at the sides of the 
ear and operating clamping jaws which run in close proximity* to 
the car rails, but normally out of contact with them. The inner 
ends of the lev 3 overlap, and in action are pressed apart by a very 
powerful spring under compression. When out of action, these 
levers are drawn together, the spring is put under compression, 
and the system locked by a trigger. Near the trigger is a centrifu- 
gal governor, operated by a an ding rope, which at a determined 
speed releases the trigger, frees the levers, and the safeties clamp 
the rails with a pressure of about 16 tons. This safety can be re- 
leased from the inside of the car. 

In the car. as has already been described, there is an automaii 
stop cont; let which operates to bring the regulator to the stop posi- 
tion and the car to rest in case the conductor removes his hand 
i m the controller because of crowding, accident or carelessness. 

On the hoisting machine there are a number of safeties. One 
which is perfectly apparent is due to the fact that the crosshead 
is moved by a screw with a heavy armature on the end of it, which 
is driven through the medium of a nut by a car of limited driving 



1 



20 

capacity. The screw itself is of forged steel, under tension and 
torsion strain.-, with a safety factor of at least i wenty to one. 

The hoisting nut. as already described, is hardened by a >pecific 
process which makes its wear very limited. In addition to this, 
there is in the nut system wlun is called a " safety nut." Normally 
this is out of contact with the thread of the screw, but it is secured 
to the hoisting nut, and >hould any accident happen to the latter, 
breaking its hold on the screw, this safety nut, the threads of which 
interlock with the screw's threads 10 a greater depth than the thread 
of the hoisting nut, would then take the place of the hoisting nut and 
-••eu ly grip tin- screw. This would put the elevator out of opera- 
tion becausi the friction between the nut and s< rew would be 
greater than the friction of the traveling crosshead, and it would 
act simply us a collar on the screw. 

The 11111 system has in addition another function. Since the 
hoisting nut i^ only held from revolving l>v its fre bion against the 
crosshead, when the nut gets to the upper limit of its travel the 
safety nut meets a solid colhn on tie row winch stops its travel 
lausing 11 and the ball-bearing nut to revolve with the screw, with- 
out, I ever, necessarily stopping the motor, and Leaving the trav- 
ling shea's to be stopped simply \>\ the w< ighl of fchi ear. 

There i till another Junction perfom ''I the nut system, that 
of a slack cable device. J I' for any reason the car in descending 

when of course the nut i* driven along by the screw, a an ob- 

truction, the p] ure □ thenui being mstantlj reduced, n recedes 

htly. alh tin irings betw< n ii and (In 3afety am to e\- 

I 'd. throwing th< atter into bad contacl with the scre^ thread* 
The nut s) a then ins oily grips the pew, revolves as a collar 

<"" 1 < ' M'< at! te us a. chi k a insl any marked moi at 

'f tl crosshi ponding i- 1 free hill of the u -1, the ropes. 

Vssumii b ever, the condition of a perfectly Cr< 1 n 1 

'" all operati ■ ties, there is a lm.it to the rate • 1 solution 

" the rew, and in ai ■ • o there 1 a rubl b iff< 1 a1 ite low< 1 
which w ild cushion it i.,, , , )lt ;||IV in|lll 

'he J limit switch, which 1 already en mentioned 
wl11 '' 1, 'dniL' !■• the motor, then i cm 

1 iin.it witch toi 1 thie 1 a 

1 both d. I( | move( 3 1, B 

'• Jl eui ,1 in h ting in the upp limn 

bra 1 mo 1 . On tl ■ n 1 ;i ,, 

illy cl 

1 ' ' ' " the d wh„h 



21 

i called a k> monitor centrifugal.*' This is for operating the brake 
when running too fast. In hydraulic elevators I here is no speed- 
operated device in case of fast running except the centrifugal on 
the car, and this is frequently .set so much above the normal sp d 
on account of the annoyance of having n operated I a temporary 
excess, as oftentimes to be useless when actually required. The 
monitor centrifugal does not throw the machine out of operation, 
but simply slows it up to any desired speed, and then allows the 
operator to resume control. 

The dynamic action of the machine is made usi of in still an- 
other way by the introduction of an "automatic chokins circuit" 
I'd 3Witch operated by the same circuits governing the main brake. 

It is in constant play and closes the circuit around the armatun 
and its series coils through a rheostat under any of the following 
circumstances: At each stop from up or down: when running down 
fast enough to work centrifugal on the machine; on failure of the 
hoisting current, or on failure of the line current. 

So positive is the control over the motor, no matter whether it 
be operating to hoist the ear or retard it in going down, that the 
brake band can actually be removed and the car still controlled 
and even with the brake in normal position the change from one 
position to another can be made so promptly that it will remain 
inactive. 

Such is the machine which has been developed during (lie past 
three years, and whose first application in a large battery in the 
Postal Telegraph Building seems destined to have the same effect 
on the elevator industry that the plant at Richmond has had on 
the railw ay industry. It is only permitted to me, of course, t o make 
the briefest allusion to this, but as illustrating in some degree the 
stent of this industry, buildings of from five to twenty-one stories 
In height are being equipped with batteries of from one to twenty- 
six machines of various types, and the business of a single company 
mploying some two or three years ago a handful of men, now 

mand- a constantly increasing force already numbering nearly 
five hundred. 






1